The present invention relates to heart valve replacement and, in particular, to sutureless prosthetic heart valves. More particularly, the present invention relates to systems, devices and methods for sizing and for identifying optimal decalcification levels at an annulus site prior to positioning of sutureless prosthetic heart valves.
Prosthetic heart valves may generally belong to one of three categories: surgical valves, transcatheter valves and sutureless valves. Transcatheter valves are typically collapsible to a relatively small circumferential size and can be delivered into a patient less invasively than valves that are not collapsible. A collapsible valve may be delivered into a patient via a tube-like delivery apparatus such as a catheter, a trocar, a laparoscopic instrument, or the like. This collapsibility can avoid the need for a more invasive procedure such as full open-chest, open-heart surgery.
In contrast to transcatheter valves, surgical valves and sutureless valves are typically delivered to a patient via open-heart surgery. Surgical valves are usually delivered to the site of implant and a portion of the surgical valve, typically an outer rim, is sutured to patient tissue. Sutureless valves, on the other hand, typically include a stent to anchor the valve in place instead of sutures. Because sutureless valves do not require lengthy suturing to patient anatomy, they are generally implanted in less time than surgical valves, resulting in less time on a bypass machine and a reduced risk of infection.
Despite the various improvements that have been made to the sutureless prosthetic heart valve implantation process, conventional methods of implanting heart valves suffer from some shortcomings. For example, in conventional techniques, clinical success of a heart valve is dependent on accurate deployment, anchoring and acceptable valve performance. Inaccurate sizing and positioning of the heart valve decreases performance and increases risks such as heart valve migration, which may result in severe complications due to obstruction of the left ventricular outflow tract and may even result in patient death. Additionally, the extent of calcification of the implant site may also affect performance. For example, calcification of the aortic valve may affect anchoring within the native aortic valve annulus such as by causing ovalization of the implanted valve which can lead to paravalvular leaks. The interaction between the implanted valve and the calcified tissue is believed to be relevant, in addition to anchoring the valve in place, to preventing valve migration and leakage.
Without being bound to any particular theory, it is believed that improper anchoring of the valve may occur due to a mismatch between the size of the native annulus and the size of the prosthetic valve (e.g., using a small heart valve size in a large annulus), lower calcification levels in the native tissue than actually predicted, or improper positioning of the valve resulting in insufficient expansion of the valve diameter. Moreover, overestimation of the annulus size may cause an oversized valve to be implanted, leading to local complications in the, for example, the aortic root, including coronary orifice obstruction, aortic dissection and heart blockage. Additionally, oversized valves may cause extended compression and/or stent deformation that affects valve durability.
In addition, incorrect sizing of a valve due to anatomical variations between patients may require removal of a fully deployed heart valve from the patient if it appears that the valve is not functioning properly. Removing a fully deployed heart valve increases the length of the procedure and increases the risk of infection and/or damage to heart tissue. Thus, systems, methods and devices are desirable that would reduce the likelihood of removal. Systems, methods and devices are also desirable to reduce negative side effects caused by improper anchoring.
Current methods for estimating the size of a patient's anatomy include imaging techniques such as transthoracic echocardiograms, trans-esophageal echocardiograms and angiography. These imaging methods are not standardized and may yield inconsistent results due to the elliptical shape of the target anatomy. Additionally, none of these techniques allow for contact forces between the annulus and stent to be measured and do not account for calcification.
There, therefore, is a need for further improvements to the devices, systems, and methods for positioning and anchoring of prosthetic heart valves. Specifically, there is a need for further improvements to the devices, systems, and methods for accurately measuring the native annulus dimensions and calcification levels in a patient. In particular, there is the need to be able to identify optimal decalcification levels at an annulus site prior to a valve implant so as to maximize valve durability by reducing the degree of ovalization and minimize the risk of migration ensuring safe anchoring of the valve due to the presence of sufficient calcification. Such accurate measurement will thus help to reduce the risks associated with valve migration and improper valve positioning. Among other advantages, the present invention may address one or more of these needs.